April 23, 2010 -- A potentially deadly airborne fungus, widely dubbed the
killer fungus, has infected more than 50 people in the U.S., according to the
CDC, and is expected to spread from the Pacific Northwest where it first
surfaced.

Even so, public health officials say, there is cause only for concern and
awareness, but not for alarm.

The killer fungus, which first surfaced in Canada in 1999, appeared in the
U.S. in Washington in early 2006. Since then, reports of cases have occurred in
Oregon and Northern California.

The fungus species triggering the infection is Cryptococcus gattii,
which can cause pneumonia or meningitis. But the infection "simply is not
common enough for people to warrant changing behavior," Harris says. "It's
still very rare. People should be concerned but not alarmed."

At a news briefing Friday, Katrina Hedberg, MD, MPH, interim state
epidemiologist for the Oregon Department of Health Services Public Health
Division, told reporters that it's also rare that people exposed to the fungus
end up getting sick.

While the CDC wouldn't specify the number of deaths, citing incomplete data,
Hedberg says that "of the 50-plus cases, around 10 of them have died."

Twelve of those 50 cases, including three deaths, have been in the state of
Washington, according to Nicola Marsden-Haug, MPH, an epidemiologist with the
Washington State Department of Health, Shoreline.

Marcia Goldoft, MD, a medical epidemiologist with the department, urges
people to keep the threat in perspective. "The benefits of outdoor activity and
exercise far outweigh the risks of a rare disease such as C.
gattii."

Tracking the Fungus

Researchers in the U.S. have been studying the fungus, traditionally located
in tropical locations, for several years, says Joseph Heitman, MD, PhD, chair
of the department of molecular genetics and microbiology at the Duke University
Medical Center in Durham, N.C.

The fungus, he tells WebMD, "originates in soil and is associated with
certain tree species, and becomes airborne."

While the fungus was typically seen in tropical areas of South America and
other tropical and subtropical regions, it surfaced in Vancouver Island,
Canada, in 1999, says Heitman, the senior author on a report on the fungus
published online this week in the journal PLoS Pathogens.

"It is a microbial pathogen that can cause significant illness and even
death, but it is very uncommon," he says.

Infections can be treated with antifungal agents, but no vaccine is
available for C. gattii, Heitman says.

The first recorded U.S. case was in Orcas Island, Wash., Heitman says. That
was followed by cases in Washington and Oregon.

Heitman's team has discovered a new pathogenic strain of the fungus in the
Oregon cases.

Unlike another fungus type, Cryptococcus neoformans, which typically
infects those who are HIV-positive or other immunocompromised people, the C.
gattii fungus can infect apparently healthy people.

The 50 cases reported to the CDC, Harris says, include people from age 15 to
95.

How the Fungus Spreads

"The fungus is present in the environment," Hedberg says. "It's present in
soil or in trees." As trucks transport lumber down the I-5 corridor in the
Pacific Northwest, she says, the fungus has likely spread.

The airborne fungus is inhaled. "People have to inhale it to get sick,"
Hedberg says. "It's not spread from person to person at all."

And, she adds, many are exposed but few actually get sick.

The time from exposure to the fungus to onset of symptoms varies, Heitman
says. It could be two to eight months.

Fungus Symptoms

Four symptoms are typical of infection with C. gattii, says Harris of
the CDC. They include: